Supercharged internal combustion engines comprising a turbocharger or a supercharger coupled to an exhaust manifold to receive exhaust gas may increase the engine's power output. The turbine of the supercharger is provided in the exhaust-gas discharge system. Impulse supercharging at low loads and/or low speeds may increase the turbine rotational speed, which can fall during idle operation and/or low load. Ram supercharging at high loads and/or high speeds may be beneficial under steady state operation of the engine.
One approach to provide the turbocharger with exhaust gas is to merge the exhaust lines of the cylinders to form a first group and second group such that the dynamic wave phenomena in the exhaust lines of the cylinders of a group have the least possible adverse effect on one another. Another approach is to merge the exhaust lines of the cylinders into a single overall exhaust line upstream of the turbine. Further, concepts are known in which the two exhaust manifolds can be connected to and separated from one another.
A potential issue with the above approaches noted by the inventors is that when exhaust lines of cylinders are merged into a first and second group the charge exchange may interfere detrimentally with one another. This approach may prohibit the turbine to be operated optimally at high loads. Another potential issue noted by the inventors is a single overall exhaust line provides a large volume of exhaust gas upstream of the turbine and may impair turbine operation at low exhaust gas flow rates. Further, connecting exhaust manifolds may lead to a residual gas problem and knocking being abetted.
One potential approach to at least partially address some of the above issues includes a supercharged internal combustion engine comprising at least one cylinder head with at least two cylinders, in which the cylinders have at least one outlet opening for discharging the exhaust gases out of the cylinder via an exhaust-gas discharge system, and the outlet opening is adjoined by an exhaust line. The at least two cylinders may be configured in such a way as to form two groups with at least one cylinder per group, the exhaust lines of the cylinders of the cylinder groups merge to form an overall exhaust line such that an exhaust manifold is formed. The two overall exhaust lines may be connected to a two-channel turbine, which comprises a rotor which is mounted on a rotatable shaft in a turbine housing, such that one overall exhaust line is connected to one of two inlet openings of the turbine wherein the inlet openings may be adjoined by one channel of the turbine and the two channels separated from one another as far as the rotor by means of a housing wall, such that the exhaust-gas streams of the two channels may be conducted separate from one another to the rotor. The two channels of the turbine can be connected to one another within the turbine housing by virtue of at least one flow transfer duct upstream of the rotor and downstream of the inlet openings being opened up, for which purpose a shut-off device is provided which has at least one adjustable shut-off body wherein the at least one shut-off body, in a rest position, separates the two channels of the turbine from one another, in a first working position, connects the two channels of the turbine to one another by opening up the flow transfer duct, and in a second working position, connects the two channels of the turbine to one another by opening up the flow transfer duct and opens up a blow-off line which branches off from the exhaust-gas discharge system upstream of the rotor.
Another potential approach to address the above issues is a method for an engine comprising adjusting a shut-off body positioned within a flow transfer duct within a turbine housing upstream of a rotor and downstream of two inlet openings from a rest position to a working position to fluidly couple two channels of the turbine housing to one another via the flow transfer duct responsive to exhaust gas flow rate over a threshold. Further, the method may adjust the shut-off body based on a time increment for the exhaust gas flow rate thresholds. Such an approach may allow the turbine to be operated optimally at low loads and high loads.
Another potential approach to address the above issues is a method for an engine with a shut-off body positioned within a flow transfer duct within a turbine housing comprising using an engine controller to switch the shut-off body in stages and/or a continuously variable fashion. The control element may switch the shut-off body from a rest position, where the shut-off body is abutted to the housing wall closing the flow transfer duct and blow-off passage, to a first working position, where the shut-off body opens the flow transfer duct while still closing the blow-off passage, when an exhaust gas flow rate is above a first threshold. The control element may switch the shut-off body from the rest position or the first working position to a second working position, where the shut-off body opens the flow transfer duct and the blow-off passage, when an exhaust gas flow rate is above a second threshold. The control element may switch the shut-off body from first or the second working position when an exhaust gas flow rate is below a third threshold. Further, the method may adjust the shut-off body using the control element after the exhaust flow rate has met a threshold for a corresponding time increment. By switching in stages, the shut-off body either closes off or opens up the flow transfer duct and/or the blow-off line, which simplifies the control and, in particular, offers cost advantages. A further option is switching in a continuously variable fashion which may reduce torque drop.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.